New records for the Helius Lepeletier & Serville fauna (Diptera, Limoniidae) of China

Abstract Background The genus Helius Lepeletier & Serville, 1828 is globally distributed with 232 species and subspecies, of which 25 have been known to occur in China. Amongst the Chinese Helius crane flies, 24 species are distributed in southern China. The species diversity of Helius in other Chinese regions may be severely underestimated due to a lack of investigation. Some investigations on crane flies in Inner Mongolia, China have been initiated by the authors together with other entomologists, with Helius being one of the key targets of attention. New information Two Helius species, H. (Helius) flavus (Walker, 1856) and H. (H.) gracillimus Alexander, 1938, are added to the Chinese fauna. The two newly-recorded species also represent the first records of the crane fly tribe Elephantomyiini in Inner Mongolia. Re-descriptions and illustrations of the two newly-recorded species are presented.

According to Oosterbroek (2023), 25 Helius crane fly species have been recorded from China, of which 23 belong to the nominotypical subgenus and two belong to the subgenus Eurhamphidia Alexander, 1915(Alexander 1915).In this study, we report two additional Helius species to the Chinese fauna, namely H. (Helius) flavus (Walker, 1856) and H. (H.) gracillimus Alexander, 1938, which also represent the first records of the crane fly tribe Elephantomyiini in Inner Mongolia, China.Re-descriptions and illustrations of the newlyrecorded species are presented.

Materials and methods
The specimens of this study were collected by insect nets at different locations in Inner Mongolia, China (Fig. 1) and deposited in the Entomological Museum of Qingdao Agricultural University, Shandong, China (QAU).Genitalic preparations of males were made by boiling the hypopygium in lactic acid (C H O ) for half an hour.Details of body colouration were examined in specimens immersed in 75% ethanol (C H OH). Specimens were examined using a ZEISS Stemi 2000-C stereomicroscope.Photographs were captured by a Canon EOS 5D Mark IV digital camera.
Head (Fig. 2B).Brownish-black.Setae on head dark brown.Antenna with scape dark brown, pedicel yellow to pale brownish-yellow, flagellomeres brown with basal segments yellow to pale brownish-yellow.Scape cylindrical, 2.5 times as long as wide.
Pedicel oval, tip slightly enlarged.Flagellomeres 1-3 oval; remaining flagellomeres cylindrical, tapering apically and elongated, with dark brown verticils.Rostrum about 1.2 times as long as remainder of head, dark brown with brownish-black setae.Palpus dark brown with brownish-black setae.
Thorax (Fig. 2C).Pronotum dirty yellow with middle area brown.Prescutum and presutural scutum yellow, darker at anterior third, dorsally a pair of yellow stripes bordered by brown dots and separated by narrow pale line.Postsutural scutum pale yellow, each lobe with oval area bordered by dark spots.Scutellum and mediotergite yellow.Pleuron yellow to brownish-yellow (Fig. 2A).Setae on thorax dark brown.Coxae brownish-yellow; trochanters brownish-yellow with fore trochanter slightly paler; femora brownish-yellow, darkened at tips; tibiae pale brown with tips dark brown.Setae on legs brown.Wing (Fig. 2D) pale brown with base and costal area yellow, wing apex slightly darkened; stigma inconspicuous.Veins brown.Venation: Sc ending opposite about 3/4 of Rs, sc-r near tip of Sc; m-m shorter than basal section of M ; cell dm about twice as long as wide; m-cu about 1/3 of its length beyond fork of M. Halter pale yellow.

Notes
Helius (H.) flavus is widely distributed in the Palaearctic Region (Oosterbroek 2023) and recorded in China for the first time.Walker (1856) first discovered this species and provided a brief description without figures and Starý (1966) illustrated the female ovipositor for the first time.Subsequently, Starý and Rozkośný (1970), Geiger (1986),  2017) provided detailed description and illustrations of the male for this species.The species is closely related to H. ( H.) unicolor (Brunetti, 1912) in the key by Xu et al. (2023) and can be distinguished by the inner gonostylus with five teeth on the outer margin of the middle (Fig. 3A, B and E).In H. (H.) unicolor, the inner gonostylus has no teeth (Brunetti 1912).
Palpus brown to dark brown with brownish-black setae, terminal segment elongated.
Thorax (Fig. 5C).Pronotum yellow with middle area slightly darker.Prescutum and presutural scutum pale yellow, dorsally with a pair pale yellow stripes separated by a narrow line and bordered by dark dots; base of lines darkened by brown.Postsutural scutum brown, each lobe with a spot indistinctly bordered by pale yellow.Scutellum brown to dark brown.Mediotergite brown with indistinct median line.Pleuron brownishyellow (Fig. 5A).Setae on thorax dark brown.Coxae yellow with fore coxa slightly darker, trochanters yellow, femora and tibiae pale brownish-yellow with tips slightly darker, tarsi brown to dark brown.Setae on legs brown.Wing (Fig. 5D) pale brown with cell sc darker; stigma large and dark brown, brown spot at base of Rs, brown seam along cord.Veins brown.Venation: Sc ending nearly at fork of Rs, sc-r near tip of Sc; m-m shorter than basal section of M ; cell dm about 2.5 times as long as wide; m-cu more than 1/2 of its length beyond fork of M. Halter brownish-yellow with knob darker.

Notes
Helius ( H.) gracillimus is an East Palaearctic species that occurs in Russia, North Korea and South Korea (Oosterbroek 2023) and now recorded in China for the first time.For descriptions and illustrations of this species, also see Alexander (1938) and Podenas and Byun (2014).The species is closely related to H. ( H.) subfasciatus Alexander, 1924 in the key by Xu et al. (2023) and can be distinguished by the brownish-yellow pleuron and the yellow coxae (Fig. 5A).In H. (H.) subfasciatus, the pleuron is dark brownish-black and the coxae is brown (Alexander 1924b).

Discussion
The two newly-recorded species for Chinese fauna are both from Inner Mongolia, a Chinese Province with very limited species records of Limoniidae.According to Oosterbroek (2023), only five limoniid crane flies are recorded in Inner Mongolia, of which four belong to the subfamily Chioneinae and only one belongs to the subfamily Limoniinae.
With the discovery of these two Helius species in this study, the number of Limoniinae species in Inner Mongolia increases to three.They also represent a new recorded crane fly tribe (i.e.Elephantomyiini) in Inner Mongolia, which indicates that the species diversity of Limoniidae in Inner Mongolia may be severely underestimated.As for Chinese Helius crane flies, previously only one species was distributed in northern China (Jilin), while the remaining 24 species were all distributed in southern China (Oosterbroek 2023).The discovery of the two Helius species in Inner Mongolia provides valuable distribution records for geographical research of the genus and also indicates that there may be huge potential for species diversity of Helius in northern China.
Figure 1.The distribution map of Helius crane flies in Inner Mongolia, China.
Femora brownish-yellow, darkened at tip.Wing with apex slightly darkened, stigma inconspicuous.Venation with Sc ending opposite about 3/4 of Rs, cell dm about twice as long as wide, m-cu beyond fork of M. Posterior margin of tergite 9 with a broad and deep V-shaped notch.Outer gonostylus with tip black and bifid.Inner gonostylus expanded near middle and bent inwards at a right angle, distal part slender; outer margin of expanded lobe with five teeth.Interbase distally horn-shaped, tip suddenly thinning into a spine.Aedeagus rod-shaped, tip slightly expanded and rounded.